The evidence is the data from the sensors, if all the other cars had 'normal' data and Ricciardo didn't then it points to an infringement and hence the penalty. Of course it could be a 'dodgy' sensor but for it to only be on the Red Bull while the Toro Rosso were fine is still a bit dubious..
Anyways Red Bull have today confirmed their
appeal, so we'll see in due course.
The DQ was the right decision, if it is found to be in error, then he's just re-instated and life goes on, although it has been several days since the event and I'm sure the sensor has been verified by the FIA, so I doubt there will be a reprieve coming.
If you read the article, it mentions that the FIA provided feedback as they probably did to other teams to adjust their flow according to the data given by the sensor, and in this case Red Bull refused to alter their flow as it believed the sensor to be in error... It may be a case of erroneous data but if all other teams obeyed and Red Bull didn't then they still deserve to be punished IMO...